Zaritok, I am on Invision so it may be different for your forum version, but in AP>General>Forum>Categories and forums. Where you have "Anime Kingdom", then look below it for "Rules and announcements". Then you click on the green cross to add your "sub forum" and name it what you want.

If you want the subforum list to be right below a forum, then go to Admin Panel>Display>Homepage>Structure and Hierarchy then look at the Hierarchy panel. Click yes on the "Sub-level links on index" option. Hope that helps!